Unless otherwise indicated herein, the materials described in this section are not prior art to the claims and are not admitted to be prior art by inclusion in this section.
In a typical cellular wireless communication system, the air interface between a base station and served access terminals may define a forward-link (or “downlink”) for carrying communications from the base station to the access terminals and a reverse-link (or “uplink”) for carrying communications from the access terminals to the base station. In various implementations, these links may be defined on or more carrier frequencies or blocks of frequencies. Furthermore, on each link, various channels may be defined through techniques such as time division multiplexing, code division multiplexing, and the like.
In one implementation, the forward-link may be divided over time into a sequence of timeslots, and the base station or associated equipment may be arranged to transmit data, such as bearer traffic (e.g., user data) and control signaling (e.g., paging and other overhead messages), to access terminals in those timeslots. In such an implementation, the base station or associated equipment may dynamically schedule transmission of data in particular timeslots and may then transmit the data according to that schedule.
To help overcome errors that may arise in wireless data transmission, the base station and served access terminals may also be arranged to apply a hybrid automatic repeat request (hybrid-ARQ or HARQ) process. In such a process, when the base station is going to transmit a data packet to an access terminal, the base station may repeatedly attempt transmission of the packet to the access terminal in sequential (e.g., interlaced) timeslots, adding more error correction coding with each subsequent attempt and/or transmitting various portions of the packet with various error correction coding in each subsequent attempt, in an effort to have the access terminal ultimately receive enough data to constitute or facilitate uncovering the packet as a whole.
By way of example, if the packet payload comprises the elements ABCD, the base station may transmit in a first timeslot the full payload ABCD plus some error correction coding. If that transmission is insufficient to allow the access terminal to uncover the payload, the base station may then transmit in a next timeslot a portion of the payload, such as ABC, plus some additional error correction coding. And if that transmission is still insufficient, the base station may then transmit in a next timeslot another portion of the payload, such as BDC, plus more substantial error correction coding. This process may continue until the packet transmission is deemed successful or until a predefined threshold number of timeslots is exhausted (in which case the transmission would have failed).
During this packet transmission process, for each transmission attempt that does not result in the access terminal having successfully received or uncovered the complete packet payload, the access terminal may transmit to the base station on the reverse-link a negative acknowledgement (NAK), to prompt the access network to engage in a next transmission attempt. On the other hand, once the access terminal has received or uncovered the complete packet (i.e., the packet transmission was successful), the access terminal may transmit to the base station a positive acknowledgement (ACK), to inform the base station that transmission of the packet was successful, thereby completing transmission of that packet.